Year	Percent
1960	10.08403
1961	9.83606
1962	12.8
1963	12.65625
1964	12.61539
1965	16.93549
1966	19.99817
1967	15.41301
1968	15.13937
1969	14.35612
1970	15.2342
1971	16.8691
1972	16.25551
1973	13.44262
1974	21.33892
1975	17.69945
1976	19.39551
1977	17.6602
1978	23.80012
1979	22.75138
1980	26.38207
1981	21.75473
1982	24.15049
1983	20.75899
1984	19.66426
1985	19.88739
1986	20.15452
1987	19.14123
1988	17.60329
1989	17.28848
1990	14.06955
1991	18.05537
1992	18.26304
1993	20.50376
1994	64.79304
1995	25.82138
1996	26.1987
1997	25.67012
1998	23.2094
1999	24.54732
2000	24.87835
2001	24.27839
2002	23.70354
2003	23.53894
2004	24.76158
2005	25.21247
2006	24.9537
2007	25.21593
2008	29.83003
2009	29.67568
2010	29.99133
2011	30.2475
2012	31.78461
2013	31.93011
2014	32.91058
2015	38.30459
2016	33.10607
2017	32.77421